The present invention relates to temperature or environmental control systems for a passenger or operator compartment of a vehicle and more particularly to a unique, manual control assembly for such systems.
Vehicles such as trucks and passenger cars typically include an environmental control or temperature control system for directing and conditioning outside air or recirculating air within the passenger or operator compartment. The systems include duct work having a fresh air inlet, a heat outlet directing air towards the floor of the compartment, a defrost outlet for directing air towards the windshield, and vent and air conditioning outlets. A heater coil or core is supported within the duct work. If so equipped, an air conditioner evaporator coil will also be positioned within the duct work. A plurality of doors are supported in the duct work for selectively directing air in the various modes of operation. Typical systems include a fresh air door, a heat door and a defrost door. Further, a blower is provided to pull air through the evaporator coil, towards the heater coil and through the outlets.
If an evaporator coil is included to cool the air within the passenger or operator compartment, the air conditioning unit will typically have two modes of operation. In a Max A/C Mode of operation, air within the compartment is recirculated through the evaporator coil. In a Normal A/C Mode, outside or fresh air plus a predetermined amount of recirculated air is passed over the evaporator coil and into the passenger compartment. When operating in a Vent Mode, air from the outside is passed directly into the compartment through the vent outlets. In the Heat Mode, outside air plus a predetermined amount of recirculated air is passed over the heater coil and towards the floor of the vehicle compartment. Typically, 70-90% of the heated air will be passed to the floor of the vehicle and the remaining percentage will be directed through the defrost outlets to the windshield. When in the Defrost Mode of operation, the majority of the air will be passed to the defrost outlets and approximately 10-30% of the air will pass to the heat outlets. When operating in a Defog Mode, the air conditioner compressor is operated and air is passed over the evaporator coils and then to the defrost outlets. A portion of the air is directed through the heat outlets and towards the floor of the vehicle compartment.
A blend air door may also be included in the duct work to proportion the amount of air passed through or around the heater coil to thereby control the temperature of the outlet air. Such systems would also include a shut-off water valve which controls flow of engine coolant through the heater coil. The shut-off water valve may be cable or vacuum actuated. Some systems do not include the blend air door but include a proportional water valve actuated through a lever and cable arrangement. The blower motor is typically controlled through a multi-position or speed blower motor switch.
Various control systems have heretofore been proposed for positioning the doors within the duct work. An example of one such system may be found in U.S. Pat. No. 3,916,988, entitled CONTROL MECHANISM FOR AN AIR-CONDITIONED DEVICE IN AUTOMOTIVE VEHICLES and issued on Nov. 4, 1975, to Metsuda. The doors in the system disclosed in this patent are positioned by a control lever integrally formed with a controlling cam mechanism. The doors are connected to the cam mechanism through cables.
Other assemblies have been proposed which automatically control the temperature within the vehicle compartment or enclosure. An example of one such system may be found in U.S. Pat. No. 4,147,205, entitled VACUUM ACTUATED AUTOMATIC TEMPERATURE CONTROL SYSTEM WITH ACTUATOR PRESSURE SIGNAL FEEDBACK and issued on Apr. 3, 1979, to Bata et al.
In still further systems which have been proposed, the doors or dampers within the duct work are positioned by vacuum operated diaphragm actuators. Vacuum from the intake manifold of the engine is selectively directed or diverted to the diaphragm actuators by a control assembly. Electrical controls are also provided for selectively actuating the air conditioning compressor and for controlling the blower motor speed.
A need exists for a relatively simple and easily manufactured control assembly for use in a vehicle environmental or temperature control system and which is capable of positioning the doors through a fluid medium. Such a system would preferably be adaptable for use in trucks or other heavy-duty equipment which have a source of pressurized air.